Attention has recently been paid to an RFID (Radio Frequency Identification) technique as a noncontact authentication technique utilizing an electromagnetic field and radio waves. According to the RFID technique, it is possible to perform authentication of a body, or the like, by reading information stored in an RFID tag (a generic designation of a medium that exchanges information by use of the RFID technique, like an IC tag and a noncontact IC card) having an antenna element in which there is mounted an IC chip worked in the form of a tag or a label through use of a reader. An UHF band and a 2.45-GHz band are currently, predominantly utilized for a radiowave RFID.
In order to enhance a characteristic, an RFID tag using a so-called “artificial medium” has recently been proposed (see; for instance, Non-Patent Document 1).